It can also save time, if it turns out (as it often does) that the only thing done with the node-set is to test whether it is empty, or to get the value of its first element.
它还可以节省时间，如果对于节点集的唯一操作就是测试它是否是空的(通常是这种情况)，或者对它的第一个元素进行赋值。
You can test for them explicitly or rely on PHP to return a default empty value when you reference them.
您可以显式地对它们进行检测，或在您引用它们时让PHP返回缺省的空值。
You can do this either by recording an interaction with the server you're testing or by creating an empty test and building it from scratch.
您可以通过记录与您测试的服务器之间的交互或是创建一个空的测试并通过手工添加测试元素来构建它。
You can also create an empty database unit test and add code later to test other types of database objects.
您也可以建立一个空的资料库单元测试，稍后再新增程序码以测试其他类型的资料库专案。
You can also create an empty database unit test and add code later to test other types of database objects.
您也可以建立一个空的资料库单元测试，稍后再新增程序码以测试其他类型的资料库专案。
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